Direct substrate bonding is an attractive technique for integrating materials of dissimilar lattice constants and/or crystal structures. Direct substrate bonding can be performed using a number of different prior art methods, but each prior art method has drawbacks. Two of these methods are performed by bringing substrate surfaces into contact with surfaces that have either been chemically treated, or plasma etched. Following each of these procedures, the substrate surface is annealed at a high temperature. As disclosed in Bengtsson, Journal of Electronic Materials, Vol. 21, No. 8 “Semiconductor Wafer Bonding: A Review of Interfacial Properties and Applications,” Mar. 6, 1992 pp. 849, one of the main disadvantages to using treatment chemicals is that because the substrate is treated while exposed to the atmosphere, the substrate is prone to having an oxide, a carbon, or another particle contaminant present on the substrate. In addition, as disclosed by Takagi, Maeda, Chung, Suga, in Sensors and Actuators, “Low-temperature direct bonding of silicon and silicon dioxide by the surface activation method,” Feb. 3, 1998, pp. 168-169, the main disadvantage to using plasma etching, is that plasma etching results in surfaces with a rough morphology. Furthermore, both chemical processes and plasma etching are intended to remove material. They do not provide a substrate surface specifically intended for bonding.
As a result, there is a need for a method of preparing a substrate surface for bonding, which eliminates oxide on the surface of the substrate, maintains a high quality crystal structure, and provides a surface with atoms specifically for bonding.